Permanent magnet construction



Jan. 17, 1939. R. REEsE ET AL 2,144,546

PERMANENT MAGNET CONSTRUCTION Filed March 9, 1938 Inventors: RudolfReese. Hans Hutti W .J

cnw n P O t t A .m e h T H IIF A 4 m b M AJUSTABLE TEMPERATURECOMPENSATION SHUNT NON MA GNET/C D CAST TER/AL Patented Jan. 17, 19392,144,546

UNITED STATES PATENT OFFICE PERMANENT MAGNET CONSTRUCTION Rudolf Reese,Berlin, and Hans Hiittig, Berlin- Pankow, Germany, auignors to GeneralElec:

tric Company, a corporation of New York Application March 9, 1938,Serial No. 194,870 In Germany May 5, 1937 4 Claims. (Cl. 175-21) Ourinvention relates to improvements in per- H are provided and fittedthrough an opening manent magnets, particularly those used for oropenings in the yoke part III and enter well damping magnets in metersand the like, and it into the die-cast material as shown in Fig. 5. hasfor its object an improved construction Such holding screw is preferablyinserted in which minimizes grinding operations, facilitates place priorto the die-casting operation. Howadjustment of magnetic strength andprovides for ever, the screw hole in the yoke may also be usedtemperature; \compensation where that is desirto insert the die-castingmaterial and the screw able. hole is then subsequently bored out andtapped The features of our invention which are beand the screw inserted.The bar magnet II is lieved to be novel and patentable will be pointedthus secured to the inner surface of one limb of 10 out in the claimsappended hereto. For a better the yoke l0 and extends towards the otherlimb understanding of our invention reference is made to form the airgap at H. in the following description to the accompanying The screw 15,Figs. 1 and 6, may comprise a drawing. Fig. 1 represents a plan view ofa screw for adjusting the strength of the magnet.

1 permanent magnet structure embodying our in- For example, if thedie-cast material l6 be of vention; Fig. 2 may represent a sectionalview non-magnetic material as is preferable and the taken on. line 2-2,Fig. 1, prior to the final unitscrew ii of magnetic material, the depthto ing of the iron yoke part It and bar permanent which the screw [5 isadjusted along the magmagnet part II; Fig. 3 represents a section ofnetic axis will vary the strength of the flux bar magnet part II takenon line 3--3, Fig. 2; crossing the air gap at H, Fig. 2. If the screw 3Fig. 4 is a plan view of the bar magnet part ll; 15 be fully inserted,it will shunt more or less and Figs. 5 and 6 are fragmentary sectionstaken of the flux between the opposite poles of the on line 5-5 and 6-6respectively of Fig. 1 and permanent magnet and decrease the flux whichrepresenting holding and compensating features passes about the yokeportion l0 and crosses the to be described. air gap. Then, by raisingthe screw l5, it will The main parts of the magnet here illustrated haveless and less shunting eifect and the flux comprise a horse shoe shapedmagnetic yoke part across air gap i! will be increased. Such ad- Ill anda permanent magnet bar part II. The justable screw may be of a magneticmaterial yoke part I0 is made of a relatively inexpensive havingconstant permeability with temperature suitable magnetic iron or softsteel that can be change in which case it will. merely serve to readilyformed into the shape desired, and maadjust the magnetic strengthindependently of chimed. Part H is a cast bar magnet of high temperaturechanges. If temperature compensacoercive force material which ispermanently tion is desired another screw vertically adjustablemagnetized along one axis as indicated by the in opening I! may be madeof a magnetic mate- 5 poles designated N and S, Fig. 2. It is providedrial having a positive or negative temperature cowith a central axialcavity or opening I! which efllcient of permeability. For example, ascrew is preferably oblong in shape as indicated in Fig. made of aniron-copper-nickel alloy will have a 4. This opening may extend throughthe magnet negative temperature coefilcient oi permeability. but wegenerally prefer to close the lower end When fully inserted in itsopening, such screw as indicated, in Figs. 2 and 3. This cavity is willshunt flux between the ends of the per- 40 formed during the castingoperation and its inmanent magnet. This shunting efiect will deteriorsurface is generally rough and is prefercrease with rise in temperatureand hence, comably larger in one dimension at the bottom end pensate theentire magnet structure for the to secure a. dove-tail efiect as bestillustrated in tendency of such a magnet to decrease in Fig. 3. It isonly necessary to grind the end polar strength with temperature rise.Then, by raising 45 surfaces of this bar magnet casting. After the thescrew, this compensation may be decreased parts iii and II have beenformed to the proper until just the desired temperature compensationshape and dimensions, these parts are united by is obtained. At the sametime the proper filling the cavity II by suitable material by a strengthof magnetic field at a given temperature high pressure die-castingoperation. The diemay be obtained by adjustment of screw I5.

cast material is preferably non-magnetic and The temperaturecompensation desired may can be readily machined. The yoke i0 is pro-'be predetermined by experiment and a nonvided with o e or re o e s l3opposite adjustable temperature compensating member of cavity I! throughwhich the die-casting material the required characteristic may beinserted in is forced. One or more holding bolts or lag screws thecavity of the permanent magnet prior to the an otherwise relativelyinexpensive magnet construction. They are suitable for use with barpermanent magnets generally, independent of the use of a yoke part suchas part Ill. The yoke l may be provided with one or more bolt holes I!for securing the same to the meter or other device on which it is used.

In accordance with the provision of the patent statutes, we havedescribed the principle of operation of our invention together with theapparatus which we now consider to represent the best embodiment thereofbut we desire to have it understood that the apparatus shown is onlyillustrative and that the invention may be carried out by other means.

2. A permanent magnet comprising a barshaped permanent magnet comprisinga casting of high coercive force magnetic material polarized along oneaxis, said casting containing a cavity extending along its polarizedaxis containing non-magnetic die-cast material, and a shunt for saidmagnet supported in said diecast material said shunt being made of amagnetic material the permeability of which varies with temperaturechanges.

3. A permanent magnet comprising a casting of high coercive forcemagnetic material, polarized along one axis, a cavity extending from oneend nearly through said casting along said axis, a non-magnetic die-castmaterial filling said cavity, and a shunt for said magnet in the form ofa screw threaded into said die-cast material along said axis, said shuntbeing made of a magnetic material the permeability of which varies withchanges in temperature.

4. A permanent magnet comprising a barshaped casting of high coerciveforce magnetic material polarized along one axis, a cavity extendingthroughout the greater length of the magnetic axis of said magnet, saidcavity being filled with a machinable non-magnetic material containing apair of parallel,'threaded screw holes extending in the direction ofsaid axis, an adjustable screw made of a constant permeabilitymagneticmaterial threaded in one hole and an adjustable screw made of a magneticmaterial having a temperature coeflicient of permeability which varieswith temperature threaded in the HANS Humor.

